1. Field of the Invention
The field of art disclosed herein pertains to thermal management systems, and more particularly the passive movement of heat energy between opposing surfaces by employing passive-acting elements such as shape memory materials.
2. Description of the Related Art
In its most basic form, thermal management and the control of heat energy is the maintenance of a given system's surfaces and components within an appropriate temperature range despite changing heat loads and variations in the thermal environment. Efficient thermal management systems have long been an issue for the National Aeronautics and Space Administration (NASA) in both ground and space-based aerospace applications. Earth orbiting spacecraft and space mission components require thermal stability during system operation, while future extraterrestrial bases will require heat management to control habitat temperatures, life support systems, and equipment.
Aerospace thermal management systems technology development is focused on the development of systems that reduce mass—thereby reducing the cost of spacecraft propulsion—and are capable of handling high heat loads with fine temperature control. The reduction of mass is integral with effective use of energy: the energy required to leave Earth's gravity, to provide space propulsion, to provide electrical power, to meet life support needs, to power scientific apparatus, and to power industrial production plants in future exploration bases. Additionally, with respect to cryogenic systems, solutions are especially limited due to the challenges of operating at extreme cold temperatures. However, there will continue to be a need for cryogenic systems as long as chemical propellants are the most efficient primary propulsion systems used in space. The performance and efficiency of cryogenic systems will have to significantly increase in order to enable the missions NASA hopes to undertake in the next twenty years.
Researchers have developed technologies such as gas-gap, paraffin wax thermal batteries, heat pipe systems, and differential thermal expansion thermal switches in response to the need for solutions to the specific challenges related to the high energy, energy dense, or energy efficient systems of all kinds. Some thermal switch devices have been developed for low-temperature cryostat (cryogenic) systems that can provide heat conduction at discrete points, but not broad area surfaces. However, the current systems require reliance upon active controls, sensors, pneumatics, hydraulics, powered pumps, heaters, and other complex devices which increase system mass, cost, and potential failure modes. Thus, there remains a considerable need for multi-functional, intelligent systems and methods that can offer significant mass and power savings along with increased reliability over a wide range of heat loads in varying environments.